Valve plate for axial hydraulic piston pump or motor

ABSTRACT

A valve plate for a axial hydraulic unit where the mass of the front side is equal to the backside and the masses of the front side and the backside are equally distributed over the area of the sides of the plate. This improvement makes the manufacturing costs higher but significantly reduces the operating costs which makes it more economical.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

[0003] Not Applicable

BACKGROUND OF THE INVENTION

[0004] This invention relates to a valve plate applicable to axialhydraulic pumps/motors.

[0005] In axial hydraulic piston pumps, of fixed or variabledisplacement, valve plates are used to channel the flow of fluid fromthe barrel, which may contain multiple pistons, to the outlet ports inthe port head. There are some instances where there are a multiple ofvalve plates. These are usually referred to as the bearing plate or theport plate. Since these plates function the same as the valve plate, thenomenclature “valve plate” will be used to refer to all.

[0006] Valve plates have certain characteristics. The front side of theplate, or the side facing the barrel face, has bearing pads [2]arraigned along the outside diameter, an inner bearing area [3], and amultiple of kidney ports [1]. The bearing pads [2] provide more area forthe hydraulic float and for stabilization. The inner bearing area [3] iswhere the hydraulic fluid separates the valve plate from the face of thebarrel. Kidney ports [1], which are machined through the plate, are theports which are used to channel the fluid from the barrel to the porthead. These kidney ports [1] usually have “fishtails” which are used toreduce cavitation of the fluid flow. Fishtails are explained by Moon,Jr. in U.S. Pat. No. 3,585,901.

[0007] The front side valve plate [FIG. 1] is separated from the face ofthe barrel [5] by a thin film of fluid [6]. This acts both as a seal forthe hydraulic fluid and as a bearing medium. As the barrel [4] rotates,the piston pushes the fluid through the barrel face [5] and through thekidney ports [1] of the plate valve. The barrel [4] is held against thevalve plate by spring tension. Only this thin film of oil [6] keeps thebarrel face [5] from touching the front side of the valve plate. Thebackside of the valve plate is pinned or fastened to the port head face[8]. The barrel face [5], the front and back sides of the valve plateand the face of the port head [8] must all be lapped to within one lightband of green achromatic light (0.0000116 in.). This flatness isimportant in order to maintain the seal between the valve plate and thebarrel face [5] and to maintain hydraulic float.

BRIEF SUMMARY OF THE INVENTION

[0008] In prior art, little concern is given to the backside of thevalve plate. Since the inner bearing area [3] is not needed on the backside of the valve plate and the outer bearing area is used only forstabilization, and since machining costs are a concern, the back face isusually left blank except for the kidney ports [1] and the machiningnecessary for the shaft.

[0009] This lack of attention given the backside of the valve plate hasled to many problems. As the temperature of the hydraulic fluidincreases, the heat from the fluid is absorbed by the front and backsides of the valve plate at different rates. If the mass of one side isgreater than the other, the side with the lesser mass will move inrelation to the side with the greater mass. Since the film of fluid [6]that separates the barrel face [5] and the front side of the valve plateis measured in millionths of and inch, it takes only the slightest of amovement for the surface tension of the fluid to be broken. Once thesurface tension is broken the valve plate can lift and separate from theface of the barrel [5] due to the influx of hydraulic fluid between thevalve plate and barrel face [5] caused by the high pressure involved.Once this lift and separation occurs the seal between the barrel face[5] and the valve plate is removed the pump can experience the loss ofoil and the loss of oil pressure resulting in lower pump efficiency. Themovement of the valve plate can also result in the valve plate cominginto contact with the barrel face [5]. The touching of the valve plateto the barrel face [5] while the unit is operating can cause scorching,shallow or deep scratches, gouges, or galling depending on the amount ofmovement. If this happens, both the barrel face [4] and the valve platewill have to be relapped or replaced depending on the amount of damage.This problem increases the cost associated with axial hydraulic pistonpumps and motor due to the cost of overhauling the unit and due to thecost in time the unit is not use. This more than outweighs the costassociated with the additional machining of the backside of the valveplate.

[0010] It is the object of the present invention to provide a valveplate where the mass of the front side [FIG. 1] and the mass of backside of the valve plate [FIG. 2 are equal and whose masses are evenlydistributed over the surface of each side of the valve plate.

[0011] By reducing the amount of movement of the valve plate it improvesthe bearing efficiency, makes for a better seal, and helps maintaindesign tolerances. The damages such a movement can cause to the barrelface and the valve plate is therefore minimized.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE INVENTION

[0012]FIG. 1 shows the front side of the valve plate.

[0013]FIG. 2 shows the back side of the valve plate.

[0014]FIG. 3 shows a block diagram of the placement of the valve platein the system.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The easiest way of machining the valve plate to obtain the equalratio of masses is to mirror the backside of the valve plate [FIG. 2] tothe front side [FIG. 1]. Although, any configuration which maintains theratio of the mass of the front side to the mass of the backside andevenly distributes that mass equally of the front and back surfaces ofthe valve plate will maintain the same efficiency.

I claim:
 1. A valve plate used in an axial hydraulic piston pump/motorwhich is made of a hardened material where the mass of the front side ofthe valve plate and the mass of the backside of the valve plate areequal within design tolerance limitations and said masses are equallydistributed over the surfaces of the front and back side of the valveplate.